Many types of electronic devices include cooling fans. In electronic devices, such as media playback systems, fan noise can interfere with users' audio experiences. Different solutions to reducing fan noise include, for example, temperature-sensing control systems that can keep cooling fans silent until they are needed. Also, quiet fans such as “feather” fans have been developed that make minimal noise. However, in high-power systems such as certain audio-visual systems, fans must run at high RPMs. Therefore, even quiet fans can generate significant noise.
Audio-visual systems are often stored by consumers in cabinets or in built-in wall units. Space-consciousness motivates consumers to keep their systems in small confined spaces. Accordingly, cooling stored devices by convection is restricted, and therefore, their cooling fans may run quite a lot, generating significant noise. Temperature-sensing control systems may operate to keep the devices cool, however, at the expense of interfering with the audio content of the media. Accordingly, a user's audio experience may be impaired, particularly when the audio output level is low.
Certain systems may utilize, for example, an ambient noise detector to sense fan noise that in turn can control a fan by activating, deactivating, or varying the speed of the fan. An ambient noise detector may sense the audio output level of the media as it is playing to regulate the fan noise. However, since fan activation requires a specific amount of time before the fan is fully operational as well as a specific amount of time before the fan is finally stopped, a system including an ambient noise detector to regulate fan noise may only partially avoid the fan noise, particularly during quiet moments in the audio output of the media. In using ambient noise to control the fan, there is no time to accelerate the fan so the air flow may be latent. The lack of synchronization with the audio output of the media by monitoring the ambient noise of the media does not resolve fan noise interference, particularly during quiet moments of the audio output.